Rename crates to cockpit

[nightkr]

Description

Fixes #29.

Also organizes the Rust crates into rust/ (to align with the other Stackable repos), moves libcockpit out of the root folder (which should help avoid silly stuff like including node_modules/ in its build closure), and moves the Helm wrapper into its own crate.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Author
- [ ] Changes are OpenShift compatible
- [ ] CRD changes approved
- [ ] Helm chart can be installed and deployed operator works
- [ ] Integration tests passed (for non trivial changes)

# Reviewer
- [ ] Code contains useful comments
- [ ] (Integration-)Test cases added
- [ ] Documentation added or updated
- [ ] Changelog updated
- [ ] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [ ] Proper release label has been added

Once the review is done, comment bors r+ (or bors merge) to merge. Further information

[Techassi]

Mostly minor stuff, otherwise lgtm. Nice job!

[Techassi]

Approved.

A little off-topic: We might want to add yarn install to the web build script as it otherwise fails to run various actions, like rustdoc or clippy. We can also add the conditional to only run yarn install if node_modules is not present.